全文获取类型
收费全文 | 41212篇 |
免费 | 8845篇 |
国内免费 | 6382篇 |
专业分类
电工技术 | 1544篇 |
综合类 | 5221篇 |
化学工业 | 922篇 |
金属工艺 | 726篇 |
机械仪表 | 3504篇 |
建筑科学 | 1087篇 |
矿业工程 | 486篇 |
能源动力 | 273篇 |
轻工业 | 1044篇 |
水利工程 | 292篇 |
石油天然气 | 425篇 |
武器工业 | 520篇 |
无线电 | 10892篇 |
一般工业技术 | 3567篇 |
冶金工业 | 633篇 |
原子能技术 | 216篇 |
自动化技术 | 25087篇 |
出版年
2024年 | 367篇 |
2023年 | 903篇 |
2022年 | 1495篇 |
2021年 | 1812篇 |
2020年 | 1732篇 |
2019年 | 1418篇 |
2018年 | 1299篇 |
2017年 | 1673篇 |
2016年 | 1779篇 |
2015年 | 2163篇 |
2014年 | 2873篇 |
2013年 | 2740篇 |
2012年 | 3587篇 |
2011年 | 3670篇 |
2010年 | 3209篇 |
2009年 | 3191篇 |
2008年 | 3423篇 |
2007年 | 3516篇 |
2006年 | 2879篇 |
2005年 | 2552篇 |
2004年 | 2045篇 |
2003年 | 1622篇 |
2002年 | 1261篇 |
2001年 | 1020篇 |
2000年 | 782篇 |
1999年 | 603篇 |
1998年 | 478篇 |
1997年 | 438篇 |
1996年 | 338篇 |
1995年 | 262篇 |
1994年 | 226篇 |
1993年 | 190篇 |
1992年 | 152篇 |
1991年 | 117篇 |
1990年 | 115篇 |
1989年 | 79篇 |
1988年 | 69篇 |
1987年 | 47篇 |
1986年 | 52篇 |
1985年 | 50篇 |
1984年 | 38篇 |
1983年 | 41篇 |
1982年 | 28篇 |
1981年 | 19篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1976年 | 8篇 |
1975年 | 8篇 |
1973年 | 6篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
Attempts have been made to extend SQL to work with multimedia databases. We are reserved on the representation ability of extended SQL to cope with the richness in content of multimedia data. In this paper we present an example of a multimedia database system, Computer Aided Facial Image Inference and Retrieval system (CAFIIR). The system stores and manages facial images and criminal records, providing necessary functions for crime identification. We would like to demonstrate some core techniques for multimedia database with CAFIIR system. Firstly, CAFIIR is a integrated system. Besides database management, there are image analysis, image composition, image aging, and report generation subsystems, providing means for problem solving. Secondly, the richness of multimedia data urges feature-based database for their management. CAFIIR is feature-based. A indexing mechanism,iconic index, has been proposed for indexing facial images using hierarchical self-organization neural network. The indexing method operates on complex feature measures and provides means for visual navigation. Thirdly, special retrieval methods for facial images have been developed, including visual browsing, similarity retrieval, free text retrieval and fuzzy retrieval. 相似文献
33.
The Logarithmic Image Processing Model: Connections with Human Brightness Perception and Contrast Estimators 总被引:1,自引:0,他引:1
Jean-Charles Pinoli 《Journal of Mathematical Imaging and Vision》1997,7(4):341-358
The logarithmic image processing (LIP) model is amathematical framework based on abstract linear mathematicswhich provides a set of specific algebraic and functionaloperations that can be applied to the processing of intensityimages valued in a bounded range. The LIP model has been provedto be physically justified in the setting of transmitted lightand to be consistent with several laws and characteristics ofthe human visual system. Successful application examples havealso been reported in several image processing areas, e.g.,image enhancement, image restoration, three-dimensional imagereconstruction, edge detection and image segmentation.The aim of this article is to show that the LIP model is atractable mathematical framework for image processing which isconsistent with several laws and characteristics of humanbrightness perception. This is a survey article in the sensethat it presents (almost) previously published results in arevised, refined and self-contained form. First, an introductionto the LIP model is exposed. Emphasis will be especially placedon the initial motivation and goal, and on the scope of themodel. Then, an introductory summary of mathematicalfundamentals of the LIP model is detailed. Next, the articleaims at surveying the connections of the LIP model with severallaws and characteristics of human brightness perception, namelythe brightness scale inversion, saturation characteristic, Weber'sand Fechner's laws, and the psychophysical contrast notion. Finally,it is shown that the LIP model is a powerful and tractable framework for handling the contrast notion. This is done througha survey of several LIP-model-based contrast estimators associated with special subparts (point, pair of points,boundary, region) of intensity images, that are justified bothfrom a physical and mathematical point of view. 相似文献
34.
本文介绍区熔单晶硅生产操作指导专家系统。首先,系统实现了连续图象的自动变周期、定瞬间采样,并提出一种新的区域扩张增量图象处理算法.其次,叙述了知识的获取过程及类规则,提出分布的多库结构,并实现了不确定性推理.最后,开发了区熔单晶硅生产操作指导专家系统,实现了从数据和图象采集、处理、事实获取、推理到给出操作指导一体化。 相似文献
35.
Enhanced Image Detection on an ARM based Embedded System 总被引:2,自引:0,他引:2
This paper presents a new technique for thedetection of Integrated Circuits within images of Printed Circuit Boards autonomouslyand without the need to be assisted by CAD data. The technique is a key partof a suite of algorithms targeted for an embedded System On Chip architecturebased on the ARM7 platform for real time detection of PCB images for diagnosticpurposes. The technique has a significant reduction in complexity when comparedto conventional approaches such as the Hough Transform. The reduction in complexitymakes the approach ideal for an embedded vision application suchas the one described in this paper. This paper presents the technique, thetarget embedded architecture and results showing the reduction in complexitywhen compared to a Hough Transform. 相似文献
36.
37.
38.
Any intelligent problem solving system should be able, given the known data on a case, to decide whether some item of information is true, false or unknown. In this paper the way in which various forms of commonsense reasoning can be integrated to provide such decisions is described. To this end three structural types of knowledge defined over data, and four strategies for exploiting these structures, are identified. ‘Decide-Status’ integrates the reasoning strategies into a task frame. This frame structure not only integrates the reasoning but also affords the appropriate facilities for providing strategic justifications for its conclusions, if required. 相似文献
39.
The main purpose of this paper is to find the mixed-mode stress intensity factors of composite materials using the crack opening displacement (COD). First, a series solution of the composite material with a crack was used to evaluate COD values. Then, the least-squares method was used to calculate mixed-mode stress intensity factors. This algorithm can be applied to any method that generates or measures COD values. The major advantage of this method is that COD values very near the crack tip are not necessary. Both finite element simulations and laboratory experiments were applied to validate this least-squares method with acceptable accuracy if the even terms of the series solution are removed. 相似文献
40.